Safety circuit for sequence start ballast with disconnect switches in the primary and secondary windings



March 8, 1966 v. M. BROOKS 3,239,716

SAFETY CIRCUIT FOR SEQUENCE START BALLAST WITH DISCONNECT SWITCHES IN THE PRIMARY AND SECONDARY WINDINGS Filed Sept. 11, 1961 United States Patent Ofitice 3,239,716 Patented Mar. 8, 1966 3,239,716 SAFETY CERCUIT FOR SEQUENCE START BAL- LAST WITH DISCONNECT SWITCHES IN THE PRIMARY AND SECONDARY WINDINGS Vern M. Brooks, Maywood, IlL, assignor to Jefferson Electric Company, Bellwood, 111., a corporation of Delaware Filed Sept. 11, 1961, Ser. No. 137,203 10 Claims. (Cl. 315138) This invention relates to safety circuits for sequence start ballasts, and in particular to the arrangement of disconnect sockets therein.

A disconnect socket is a lamp socket having two contacts therein, both of which make electrical contact with the lamp terminal, such as the terminal of an instant start lamp. Therefore, when the lamp is in place, the two contacts are of common potential; when the lamp is removed, or axially displaced incident to removal, the connection between the two contacts is broken. The disconnect socket is therefore often used to control the conditions in a circuit other than the lamp circuit. For instance, in an autotransformer circuit where one terminal of a lamp is connected to the primary, a disconnect socket is frequently interposed in one side of the line, so that displacement of the lamp incident to removal de-energizes the primary and causes the whole circuit to go dead. In this arrangement, the disconnect socket is referred to as a primary disconnect, and the arrangement is explained in greater detail in the Kulka Patent No. 2,464,643, granted March 16, 1949.

The object of a safety circuit is to avoid a potential between one terminal of a lamp and ground which would be of sufficient magnitude to cause the lamp to ignite through the body of the person who is changing lamps. This hazard exists as soon as one terminal of a lamp is displaced from its socket, incident to removal, and while the opposite terminal is still engaged in its socket. The use of a primary disconnect avoids this hazard.

However, with the development of various plural lamp circuits, it is not always possible to arrange the circuit elements so that each lamp is connected to one or the other side of the line, so as to permit the use of a primary disconnect. In other instances, it is possible to so arrange the circuit, but only by introducing some undesirable feature in the circuit design. In other words, the use of the primary disconnect feature, in many instances, materially restricts latitude of design.

One such instance occurs in the design of a sequence start ballast which is energized from a 277 volt line. When a sequence start ballast is energized from a 120 volt line, it is possible to arrange the elements so that one lamp is connected to one side of the line, and the other lamp to the other side of the line, thus permitting the use of a primary disconnect for each lamp. It is not desirable to so arrange the elements in a 277 line voltage sequence start ballast, and therefore latitude of design is seriously restricted.

It is an object of my invention to provide an improved safety circuit for sequence start ballasts which provides greater latitude of design than that heretofore available.

Another object of my invention is to provide an im proved safety circuit for a 277 volt sequence start ballast in which the operating circuit is connected to the primary winding by a tap, thus avoiding the existence of a high line voltage across coil leads during open circuit conditions which occurs when a primary disconnect is interposed in the middle of the primary winding.

A further object of my invention is to provide an improved means for rendering inoperative the starting circuit of a sequence start ballast when one end of a lamp is displaced incident to removal.

According to my invention, I have found that either lamp in itself operates as a circuit breaker with respect to the potential of the operating circuit, due to its non-conductive condition when one lamp is displaced incident to removal, with the result that the safety hazard can be eliminated if the said lamp displacement is utilized to render the starting circuit inoperative. Thus, it is possible to eliminate one or both of the primary disconnects heretofore used, with the result that greatly increased latitude in circuit design is provided.

For instance, in one embodiment of my invention, only the #2 lamp is connected to line, thus requiring only one primary disconnect; in a second embodiment only the #1 lamp is connected to line. In each instance, the displacement of the non-line-connected lamp incident to removal is effective to create the desired safety condition.

With reference now to the drawings in which like ref erence numerals designate like parts:

FIG. 1 is a circuit diagram of the two-lamp sequence start ballast embodying my invention;

FIG. 2 is a diagram similar to FIG. 1 but showing the circuit conditions as the #1 lamp is being removed;

FIG. 3 is a circuit diagram showing a modification of my invention, the core structure being omitted for the sake of clarity;

FIG. 4 is a diagram similar to FIG. 3 but showing the circuit conditions as the #2 lamp is being removed; and

FIG. 5 is a simplified diagram showing the starting circut of the FIG. 3 modification.

In all of the figures the respective circuits include a #1 lamp and a #2 lamp. Also, it will be assumed in FIGS. 1 and 3 that one side or the other of the line 11-12 will be grounded, although it is immaterial to the operation of the invention as to which is the grounded side. It neither side were grounded the hazard would not arise, but the possibility of a short circuit to ground, due to failure of insulation, calls for some connection between the secondary circuit and ground. This connection may be in the form of an autotransformer connection.

The circuit of FIG. 1 includes a primary winding 10 which is connected across line 11-12. The primary is provided with a tap 13 which divides it into portions 14 and 15. The circuit also includes an operating secondary winding 16 and a starting winding 17. The windings 10, 16 and 17 are mounted on a suitable core structure 18 which provides leakage paths between the various windings, but a greater amount of leakage is pro vided between windings 10 and 17, as indicated by the magnetic shunt 19, than exists between the windings 1t) and 16. The most convenient arrangement is to locate the primary winding 10 between the other two windings 16 and 17.

The sum of the voltages across primary portion 14 and secondary 16 is less than the starting voltage of the lamps.

As regards the #2 lamp, one of the secondaries is connected in bucking relationship with respect to the other, This general arrangement, which also includes a condenser 21, is shown in Feinberg Patent 2,558,293, granted June 26, 1951, and is referred to in the trade as a sequence start circuit.

The characteristic of this circuit is that during lamp operation, an operating circuit is provided which includes both lamps and the operating secondarylfi. The starting winding 17 forms a part of a separate circuit which develops sufficient voltage to start the #1 lamp, and then to create a phase condition with respect to the voltage induced in the operating secondary 16 which applies sufficient voltage across the #2 lamp to ignite the same. The

a bucking relationship is one of the features which provides this characteristic.

In the FIG. 1 circuit, the operating circuit includes line 11, lamp #2, operating secondary 16, lead 20 which connects the winding 16 with the condenser 21, condenser 21, lamp #1, tap 13 and primary portion 14, back to line 11.

The starting winding 17 is connected between one end 27 of lamp #1 and a junction point 22 in lead 20. Therefore, the starting circuit includes starting winding 17, condenser 21, and #1 lamp, back to winding 17.

A- primary disconnect lamp socket 23 is interposed in line 11, and afiords electrical connection between the end 28 of the #2 lamp and the line 11. Displacement of the #2 lamp incident to removal therefore deenergizes the primary winding 10, as previously described.

A disconnect socket 24 is provided for the end 27 of the #1 lamp. One of the socket contacts 25 is con nected to the tap 13, and the other contact 26 is connected to the starting winding 17. Thus, when the #1 lamp is about to be removed in the usual manner, by placing the same axially away from the disconnect socket 24, the operating circuit will be broken at the point 25, and the starting circuit will be broken at the point 26. The condition of the circuit at this time is shown in FIG. 2 in which the ground connection at the end 27 of the #1 lamp represents the body of the operator.

Assuming that line 12 is grounded, the in the operating circuit represents the sum of the line voltage across the primary plus the voltage induced in the secondary winding 16. The sum of these voltages, whereas it is sufficient to maintain both lamps in operation, is not sufiicient to ignite the same. Therefore, the circuit remains open due to the fact that the #2 lamp is non-conducting, as well as the #1 lamp. Similarly, the breaking of the starting circuit isolates the end 29 of starting winding 17 from either line and from ground. Therefore, no starting potential exists at point 22 with respect to ground, and the #1 lamp will not ignite.

If line 11 were grounded, instead of line 12, the of the operating circuit would be less. Since all points of the operating circuit have a potential with respect to ground, it is referred to herein as a grounded operating circui A modified arrangement is shown in FIG. 3 in which the corresponding parts are indicated by the same reference numerals primed. The circuit differs from the FIG. 1 circuit in that a portion of the primary winding 10' is included in the starting circuit. As shown in FIG. 3, the primary winding 10' is tapped at 30 to provide portions 31 and 32., of which the portion 32 forms a part of the operating circuit. A lead 33 connects the end 34 of the #2 lamp to the tap 30.

The starting winding 17 is connected between the point 22' and the tap 39, the leads 33 and 35 forming the connection between the end 40 of starting winding 17 and the tap 30.

The disconnect socket 36 for the #1 lamp is a primary disconnect so that removal of the #1 lamp causes the whole circuit to go dead in the same manner as previously described.

The disconnect socket 37 for the #2 lamp has contacts 38 and 39, one connected to each lead, 33 and 35 respectively.

When the #2 lamp is displaced incident to removal, the operating circuit is broken at point 38, thus rendering the #1 lamp non-conducting. The condition of the circuit at this time is shown in FIG. 4, in which a ground connection, representing the operators body, is shown at the end 34 of the #2 lamp.

As shown in FIG. 5, in which the parts are rearranged for clarification, the disconnect socket 37 is interposed in the starting circuit. Therefore, displacement of the #2 lamp breaks the starting circuit, and isolates the end 40 of the starting winding 17' from either line and from ground. Therefore, no starting voltage exists at point 22 with respect to ground and the #1 lamp will not be rendered conductive by ignition thereof.

In FIGS. 1 and 3, the direction of the open circuit induced voltage with respect to the voltage drop across the primary is shown by the dotted line arrows, the primary voltage drop being shown by the curved solid line arrow.

As a practical example of my invention, a ballast was constructed in accordance with the arrangement of FIG. 1. The primary winding consisted of 1215 turns of number 26 wire which was tapped so that the portion 14 comprised 891 turns, and the portion 15 comprised 324 turns. The operating secondary winding 16 comprised 2070 turns of number 26 /2 wire. The starting winding 17 comprised 3480 turns of number 33 wire. The comdenser 21 was 1.9 mfd. The lamps were 96 T 12 instant start lamps having a starting voltage of approximately 625, a rated operating voltage of 207, and a rated operating current of .430 ampere.

When the primary is connected across a 277 volt 60 cycle line, 207 volts is developed across the portion 14, and 471 volts is induced in the operating secondary winding 16, thus providing a total available for the operating circuit of approximately 673 volts. This is insufiicient to start both lamps.

The starting voltage induced in the starting winding 17 is 766 volts which is more than enough to start the #1 lamp, and the combined voltages across windings 16 and 17, when the phase relationship is taken into account, is suflicient to start the #2 lamp.

During operation the total voltage drop across both lamps is about 414 volts, and the voltage drop across the condenser 21 is about 620 volts.

Comparable values may be provided for the modification of FIG. 3, except that FIG. 3 requires fewer turns in the starting winding 17'.

Although only preferred embodiments of the present invention have been described herein, it will be understood that various modifications and changes may be made in the construction shown without departing from the scope of the invention as pointed out in the appended claims.

I claim:

1. In a sequence start ballast having a grounded series operating circuit which includes a secondary winding, a condenser, and socket means for making connection with two gaseous discharge devices, and also having a starting winding which is connected across one of said gaseous discharge devices and said condenser, the combination of a two-contact disconnect socket for one of said gaseous discharge devices, one of the contacts of said disconnect socket being included in said operating circuit, and means connecting the other one of said contacts with one end of said starting winding.

2. In a sequence start ballast having a grounded series operating circuit which includes primary and secondary windings, a condenser, and socket means for making connection with the opposite ends of each of two fluorescent lamps, said ballast also having a starting winding which is connected across one of said lamps and said condenser, the combination of a two-contact disconnect socket for one of said lamps, one of the contacts of said disconnect socket being included in said operating circuit, means connecting the other one of said contacts with one end of said starting winding, and a primary disconnect for the other of said lamps.

3. In a sequence start ballast having a grounded series operating circuit which includes a secondary winding, two lamps, and a condenser, and also having a starting Winding which is connected across one of said lamps and said condenser, the combination of a two-contact disconnect socket for each one of said lamps, one of the contacts of each disconnect socket being included in said operating circuit, and the other one of said contacts of one of said disconnect sockets being connected with one end of said starting winding, said one end of said starting winding being insulated from ground.

4. In a sequence start ballast having a core structure, a primary winding, a secondary winding, and a starting winding mounted in end to end relationship on said core structure, and having a series operating circuit which includes said primary and said secondary winding, a condenser, and socket means for making connection with the opposite ends of two fluorescent lamps, said starting winding being connected across one of said lamps and said condenser to provide a starting circuit, the combination of a two-contact disconnect socket for one end of one of said lamps, lead means connecting one contact of said disconnect socket with said primary winding, lead means connecting the other contact of said disconnect socket with one end of said starting winding, the other end of said starting winding being connected to said operating circuit, whereby the displacement of said lamp away from said disconnect socket incident to removal breaks said operating circuit and renders said lamps nonconductive with respect to the potential of said operating circuit so that no potential will exist between the displaced end of said lamp and ground, and whereby said displacement also breaks said starting circuit, and a primary disconnect for the other one of said lamps.

5. In a sequence start ballast having a core structure, a primary winding, a secondary winding, and a starting winding mounted in end to end relationship on said core structure, and having a series operating circuit which includes said primary and said secondary winding, a condenser, and socket means for making connection with the opposite ends of a #1 lamp and a #2 lamp, said starting winding being connected across said #1 lamp and said condenser, the combination of a primary disconnect for one end of said #2 lamp, a two-contact disconnect socket for one end of said #1 lamp, first lead means connecting one contact of said disconnect socket with said primary winding, and second lead means connecting the other contact of said disconnect socket with one end of said starting winding, the other end of said starting winding being connected to said operating circuit, whereby the displacement of said #1 lamp away from said disconnect socket incident to removal breaks said operating circuit and renders said lamps nonconductive with respect to the potential of said operating circuit whereby no potential will exist between the displaced end of said #1 lamp and ground, and whereby said displacement breaks the connection through said disconnect socket between said first mentioned end of said starting winding and said primary winding to isolate said first mentioned end of said starting winding whereby no starting potential will exist at said second mentioned end of said starting winding with respect to ground.

6. The combination as claimed in claim 5 in which said primary winding is provided with a tap, and in which said first lead means connects with the said primary winding at said tap.

7. In a sequence start ballast having a core structure, a primary winding, a secondary winding, and a starting winding mounted in end to end relationship on said core structure, and having a series operating circuit which includes said primary and said secondary winding, a condenser, and socket means for making connection with the opposite ends of a #1 lamp and a #2 lamp, said starting winding being connected across said #1 lamp and said condenser, the combination of a primary disconnect for one end of said #1 lamp, a two-contact disconnect socket for one end of said #2 lamp, first lead means connecting one contact of said disconnect socket with said primary winding, and second lead means connecting the other contact of said disconnect socket with one end of said starting winding, the other end of said starting winding being connected to said operating circuit, whereby the displacement of said #2 lamp away from said disconnect socket incident to removal breaks said operating circuit and renders said lamps nonconductive with respect to the potential of said operating circuit whereby no potential will exist between the dis placed end of said #2 lamp and ground, and whereby said displacement breaks the connection between said first mentioned end of said starting winding and said primary winding to isolate said first mentioned end of said starting winding whereby no starting potential will exist at said second mentioned end of said starting winding with respect to ground.

8. The combination as claimed in claim 7 in which said primary winding is provided with a tap, and in which said first lead means connects with the said primary winding at said tap.

9. In a sequence start ballast having a core structure, a primary winding having a tap, a secondary winding, and a starting winding, said windings being mounted in end to end relationship on said core structure, and having a series operating circuit which includes said primary and said secondary winding, a condenser, and socket means for making connection with the opposite ends of a #1 lamp and a #2 lamp, said starting Winding being connected across said #1 lamp, said condenser and a portion of said primary winding to provide a starting circuit, the combination of a primary disconnect for one end of said #1 lamp, a two-contact disconnect socket for one end of said #2 lamp, lead means connecting one contact of said disconnect socket with the tap of said primary Winding, and lead means connecting the other contact of said disconnect socket with one end of said starting winding, the other end of said starting winding being connected to said operating circuit, whereby the displacement of said #2 lamp away from said disconnect socket incident to removal breaks said operating circuit and renders said lamps nonconductive with respect to the potential of said operating circuit so that no potential will exist between the displaced end of said #2 lamp and ground, and whereby said displacement breaks the con nection through said disconnect socket between said first mentioned end of said starting winding and said tap to interrupt said starting circuit.

10. In a sequence start-ballast having a grounded series operating circuit which includes a secondary winding, two lamps, and a condenser, and also having a. starting circuit which includes a starting winding, one of said lamps, and said condenser, the combination of a two-contact disconnect socket for one of said lamps, one ofthe contacts of said disconnect socket being included in said operating circuit, and the other one of said contacts being included in said starting circuit, said disconnect socket providing a connection between said operating and said starting circuits when a terminal of said one lamp is engaged thereby, whereby the displacement of said one lamp away from said disconnect socket incident to removal thereof will break both said operating circuit and said starting circuit and will break said connection between said two circuits.

References Cited by the Examiner UNITED STATES PATENTS 2,464,643 3/1949 Kulka. 2,509,188 5/ 1950 Feinberg. 2,558,293 6/1951 Feinberg. 2,885,597 5/1959 Naster.

GEORGE N. WESTBY, Primary Examiner. C. R. CAMPBELL, Assistant Examiner. 

5. IN A SEQUENCE START BALLAST HAVING A CORE STRUCTURE, A PRIMARY WINDING, A SECONDARY WINDING, AND A STARTING WINDING MOUNTED IN END TO END RELATIONSHIP ON SAID CORE STRUCTURE, AND HAVING A SERIES OPERATING CIRCUIT WHICH INCLUDED SAID PRIMARY AND SAID SECONDARY WINDING, A CONDENSER, AND SOCKET MEANS FOR MAKING CONNECTION WITH THE OPPOSITE ENDS OF A #1 LAMP AND #2 LAMP, SAID STARTING WINDING BEING CONNECTED ACROSS SAID #1 LAMP AND SAID CONDENSER, THE COMBINATION OF A PRIMARY DISCONNECT FOR ONE END OF SAID #2 LAMP, A TWO-CONTACT DISCONNECT SOCKET FOR ONE END OF SAID #1 LAMP, FIRST LEAD MEANS CONNECTING ONE CONTACT OF SAID DISCONNECT SOCKET WITH SAID PRIMARY WINDING, AND SECOND LEAD MEANS CONNECTING THE OTHER CONTACT OF SAID DISCONNECT SOCKET WITH ONE END OF SAID STARTING WINDING, THE OTHER END OF SAID STARTING WINDING BEING CONNECTED TO SAID OPERATING CIRCUIT, WHERBY THE DISPLACEMENT OF SAID #1 LAMP AWAY FROM SAID DISCONNECT SOCKET INCIDENT TO REMOVAL BREAKS SAID OPERATING CIRCUIT AND RENDERS SAID LAMPS NONCONDUCTIVE WITH RESPECT TO THE POTENTIAL OF SAID OPERATING CIRCUIT WHEREBY NO POTENTIAL WILL EXIST BEWEEN THE DIS PLACED END OF SAID #1 LAMP AND GROUND, AND WHEREBY SAID DISPLACEMENT BREAKS THE CONNECTION THROUGH SAID DIS CONNECT SOCKET BETWEEN SAID FIRST MENTIONED END OF SAID STARTING WINDING AND SAID PRIMARY WINDING TO ISOLATE SAID FIRST MENTIONED END OF SAID STARTING WINDING WHEREBY NO STARTING POTENTIAL WILL IXIST AT SAID SECOND MENTIONED END OF STARTING WINDING WITH RESPECT TO GROUND 